Black-and-white photosensitive materials are processed after exposure in processes such as black-and-white development, fixing and water washing. A black-and-white developer is used for black-and-white development, a fixer is used for fixing and town water or ion exchanged water is used for water washing and a stabilizer is used for a stabilizing process. Each processing bath is generally adjusted to a temperature of 20.degree. to 50.degree. C. and the photosensitive material is processed by immersion in these processing baths.
Of these processes, the developing process is a process wherein a developing agent which is a reducing agent acts on silver halide grains which have been sensitive by exposure to light in a photographic emulsion and the Ag.sup.+ is reduced to Ag. The silver image in a black-and-white photograph is formed in this way.
At this time, organic compounds such as 3-pyrazolidones and hydroquinones can be used as developing agents and alkaline aqueous solutions of these compounds are generally used as developers. However, it is known that metal compounds which have reducing properties with respect to silver halide grains which have been exposed to light can be used as developing agents as well as organic compounds of this type. The metal compounds in this case include salts and complexes of transition metals such as those based on vanadium, titanium, iron, and chromium for example (in practice, when listed in terms of their atomic symbols, they include Ti, Zr, Hf; V, Nb, Ta, Cr, Mo, W; Mn, Tc, Re; Fe, Ru, Os; Co, Rh, Ir, Ni, Pb, Pt and the like) [Nippon Shashin Zasshi, 20 (2), 62 (1957); ibid 19, 40 (1956); Nippon Shashin Zasshi, 29, 31 (1966); ibid 45(1), 33 (1982); Shashin Kogyo, March, 67 (1967); Nippon Kagaku Zasshi, No.9, 1321 (1980); PSE, 19, 283 (1975); JP-B-54-41899; Chiba University Engineering Department Research Reports, 14, 1 (1962); ibid 21(40), 169 (1970); ibid, 18, 39 (1967); ibid 21(39), 11 (1970); JP-A-50-51731; U.S. Pat. Nos. 3,942,985 and 3,938,998; British Patent 1,462,972, JP-A-57-78534; PSE, 12(6), 288 (1968); PSE, 14(6), 391 (1970) etc.]. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application", and the term "JP-B" as used herein signifies an "examined Japanese patent publication".)
When compared with the organic developing agents which inevitably react with preservatives in the developer and form compounds which cannot be regenerated, these metal compounds can be regenerated by carrying out reduction electrically after development processing. Further, whereas the organic developing agents are used as alkaline liquids, the metal compounds can be used as acidic or neutral aqueous solutions with the result that the swelling of the gelatin film of the photographic photosensitive material is minimized and satisfactory processing can be achieved even when the gelating film strength of the photosensitive material is low. Moreover, the developing agent readily enters the gelatin film and development is rapid and, since the carry-over of the processing bath to the next bath is also reduced, deterioration of the next bath can also be prevented with these metal compounds. Moreover, the metal compounds have an advantage for example in that they can be used as developing agents at high concentrations, but they have disadvantages because the oxidation/reduction potential of the developer changes as the developing reaction proceeds, the activity level cannot be maintained in a stable manner, the image obtained is sometimes poor when compared to that obtained with an organic developing agent and development is slow.
Methods in which development processing is carried out while electrolytically reducing the compounds comprising metal ions of which the oxidation number is increased which are generated by the development reaction and methods in which large amounts of replenisher are used can be cited for example and methods of dealing with the problems such as those indicated above. The former electrolytic reduction method has disadvantages in respect of equipment and costs in that the electrolysis equipment is large and in that a certain amount of replenisher must be added since it is impossible to prevent accumulation of the halide ions which results in an inhibition of development. Furthermore, the latter methods in which the rate of replenishment is increased not only have a cost disadvantage but should also be avoided from the viewpoint of environmental protection. Furthermore, there are also methods wherein the developer is activated by the inclusion of a metal of the same species as the metal complex or metal ion in the developer (JP-B-54-41899) for example, but it is difficult to control the amount of metal added and the procedure is complicated.
The process for reducing a metal complex as well as removing a halide compound during treatment of the light-sensitive material is disclosed in JP-A-4-250449 and JP-A-4-243253.
Said process, however, is liable to cause disadvantages such that developing fog is liable to be caused, and in some occasion maximum density is still insufficient, and film hardness is deficient. In particular, the drawback is found that a developing process is rather slow comparing with a process using a conventional hydroquinone type developing solution.
Hence, a method where the processing performance can be maintained easily, and moreover raising the photographic speed of the image obtained by processing with the developer, reducing the fog level and, in particular, speeding up development are desirable for developers in which the developing agent is a metal compound.